Monday, February 15, 2010

D&RG's FIRST... Part five

Double steam domes... #11, "Cucharas", and #12, "Las Animas".

These two Baldwin locomotives were the last of the Class 35 2-6-0's. They both sported a second steam dome just to the rear of the stack. The idea behind such a forward-mounted dome was that a much shorter throttle pipe would increase efficiency. One must assume that it didn't pan out very well. Perhaps the savings created by the increased efficiency - if any - were not enough to justify the cost of the additional dome.

To my knowledge, these two were the only 2-6-0's the forward steam dome concept was applied to. However, the D&RG tried this forward steam dome idea on it's first three 4-4-0's in 1876.

left click to enlarge

If you look on page 18 of Robert A. LeMassena's "Rio Grande... to the Pacific!", you will see one of these locomotives and how those larger steam domes were polished to a mirror finish.

Both of these locomotives were rebuilt into Class 39 0-6-0T's, #11 Mar 1885 and #12 Mar 1884.

Since the Class designation generally indicated the tractive effort of a locomotive, upgrading the class of these units from Class 35 to Class 39 indicates - to me- more tractive effort.

To do that, they had to either:

1- Increase operating steam pressure... very risky,
2- Install larger engines... very expensive, or:
3- Improve the HP-to-weight ratio... very simple

I vote for #3. Eliminating the pilot, pilot truck and the tender would improve the HP-to-weight ratio, increasing the Class designation. But that's just a guess, since the weight of the new water tank would be substantial.

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